The present invention relates to chemical analysis. More particularly, the present invention relates to the determination of fatty acids in cooking fats and oils.
The manufacturers of cooking fats and oils recommend a maximum level of three to four percent (3-4%) free fatty acids in cooking oils. The term "free fatty acids" is used to distinguish fatty acids which are not chemically bound to glycerol moities as carboxylic esters. Fats and oils, when pure, consist almost entirely of the esters of fatty acids and glycerol. Those which are solid at room temperature are commonly referred to as "fats," and those liquid at room temperature as "oils."
As fats and oils are used in cooking, they tend to break down, degrade, and hydrolyze to free fatty acids, glycerol, and other polar materials. The free fatty acids are among the harmful products of this degradation. Many restaurants continue to use their cooking fats and oils well beyond the 3-4% recommended maximum. This is primarily because there is no accurate method for determining the percentage of free fatty acids in cooking fats and oils which is simple and quick. One method currently available is the American Oil Chemists Society (AOCS) Procedure CA5a-40, which is the standard procedure used in and by the laboratories. This procedure is summarized as follows, with milliliter(s) abbreviated as "ml", normality as "N", sodium hydroxide as "NaOH", and percent as "%".
A numerical table is used to determine the sample weight; the volume of 95% and 5% water by volume ethyl alcohol "neutralized" with alkali to a faint, permanent pink color; and the concentration of standard sodium hydroxide solution which are to be used in the test.
The designated sample size is weighed into an oil sample bottle or Erlenmeyer flask.
The specified volume of 95% hot "neutralized" ethyl alcohol and 2 ml of a 1% by weight solution of phenolphthalein in 95% ethyl alcohol are added.
The sample is then titrated with the specified concentration of aqueous sodium hydroxide, shaking vigorously until the appearance of the first permanent pink color of the same intensity as that of the 95% alcohol before the addition of the sample, "permanent" being defined as persisting for 30 seconds.
The percentage of free fatty acids, expressed usually as oleic acid, is then calculated, using the following formula: ##EQU1##
Clearly, the above method is time-consuming and requires apparatus not generally available to restaurants. What is needed is a test procedure which is reliable, accurate, simple, quick, and inexpensive. The present invention provides the apparatus and method for such a test procedure.